Eddy current workpiece surface fault detector - uses sets of energising and detection coils variously angled to direction of workpiece movements

摘要

The detector uses an energising coil (10) to induce AC in the workpiece (1) and a detection coil (11) in which a current is induced due to the magnetic field caused by the eddy current components in the workpiece (1), at the location of a fault. The energising coil (10) is angled to the direction (2) of relative movement of the workpiece (1), so that the induced AC acts in a direction (4) at an acute angle to this direction (2) of movement. The coil axis of the detection coil (11) is parallel to the direction of induced eddy currents in a workpiece without surface faults. Pref. a series of energising coils (10) and associated detection coils (11) are used, with the energising coils (10) set at varying angles to the direction (2) of relative movement of the workpiece (1).